1. Field of the Invention
The present invention relates to a pressure damper for alleviating pressure fluctuation of fluid, and more particularly, to a pressure damper in which a bonding strength between a flexible film and a main body portion is improved, and to a liquid jet head and a liquid jet apparatus that use the pressure damper.
2. Description of the Related Art
In recent years, there has been used an ink jet type liquid jet head which ejects ink droplets onto recording paper and the like to draw letters and diagrams, or ejects a liquid material onto a surface of an element substrate to form a functional thin film. The liquid jet head of this type is supplied with ink or a liquid material from a liquid tank via a supply tube, and is caused to eject the ink or the liquid material filled in channels thereof from nozzles communicated to the channels. At the time of ink ejection, the liquid jet head and a recording medium for recording the jetted liquid are moved, to thereby record the letters and diagrams or form the functional thin film in a predetermined shape. In an apparatus of this type, it is necessary to control an ejection amount and an ejection speed with high accuracy when the liquid droplets are ejected from the nozzles. The ejection amount and the ejection speed are affected by an ink pressure of the nozzles, and hence in order to fix the ink pressure, a pressure damper is provided in an ink flow path.
For example, Japanese Patent Application Laid-open No. 2009-137263 describes a damper for fixing the pressure of the ink to be ejected from a printing head. FIG. 9 is an exploded perspective view of the damper (FIG. 3 of Japanese Patent Application Laid-open No. 2009-137263). The damper includes a damper base body 120 having a recessed portion for storing ink formed therein, a flexible film portion 122 for closing an opening of the recessed portion, and a damper cover 121 provided above the film portion 122, for preventing breakage of the film portion 122. Ink flows in from an ink supply path 104 in a direction of “a”, and flows out toward a flow path member of a recording head in a direction of “b”. Inside the recessed portion, there are provided a movable plate 123 and a spring 124 provided between the movable plate 123 and the damper base body 120 (see FIG. 10).
Ink is filled in a region surrounded by the recessed portion of the damper base body 120 and the film portion 122. When pressure fluctuation is generated in the filled ink, or when pressure fluctuation is transmitted to the filled ink via the ink supply path 104, the film portion 122 is displaced in the vertical direction to alleviate the pressure fluctuation of the filled ink. With this, the pressure fluctuation is not transmitted to the ink flowing out in the direction of “b”. That is, the damper causes the ink that has been subjected to pressure fluctuation alleviation to flow out in the direction of “b”.
Generally, the damper base body 120 and the film portion 122 are made of a synthetic resin. The damper base body 120 is formed by molding of the synthetic resin, and the film portion 122 is bonded to an upper end portion of the damper base body 120 by thermal welding. Ink is filled into the recessed portion of the damper base body 120. Further, pressure fluctuation is applied to the ink filled inside. Therefore, the upper end portion of the damper base body 120 is required to be bonded to the film portion 122 with good sealing property and firmly so as to prevent ink leakage and prevent peeling of the film portion 122 even when the internal pressure of the ink greatly increases.
FIG. 10 is a schematic vertical sectional view taken along the line X-X of FIG. 9. In order to firmly bond the film portion 122 and the upper end portion of the damper base body 120 to each other and ensure the sealing property, the design is made so that a bonding area between the film portion 122 and the damper base body 120 is large. In this case, sink marks are generated at the time of molding of the damper base body 120, and recesses K are formed as illustrated in FIG. 10. Therefore, the film portion 122 cannot be uniformly bonded to the upper end portion of the damper base body 120. As a result, there have been problems in that the ink filled inside the recessed portion leaks out via the recesses K formed in the bonding surface, or, when the bonding strength reduces and the ink internal pressure increases, the film portion 122 peels off from the upper end surface of the damper base body 120.